Best practice for own TypeChecker that overrides is_type

[sebastianw]

Hello,

I'm trying to ignore type checking for a specific class instance that represents a Link in our YAML Schema. Right now I'm creating a new type checker, but to make it work as expected I have to create it with the "original" types taken from the private instance attribute _type_checkers of the original type checker.

Is this the best way to override the is_type function of a TypeChecker? I didn't want to monkey patch the function in the original TypeChecker.

class LinkTypeChecker(jsonschema.TypeChecker):
    """
    A Custom jsonschema TypeChecker that always returns True for our custom Link class.
    """

    def is_type(self, instance: Any, type: str) -> bool:
        if isinstance(instance, YamlLink):
            log.trace(f"Ignoring type validation for {instance}")
            return True
        return super().is_type(instance, type)


def extend_validator(validator: type[jsonschema.Validator]) -> type[jsonschema.Validator]:
    _old_types = validator.TYPE_CHECKER._type_checkers
    validator = jsonschema.validators.extend(validator, type_checker=LinkTypeChecker(_old_types))
    return validator

validator_cls = jsonschema.validators.validator_for(schema)
# noinspection PyTypeChecker
validator_cls = extend_validator(validator_cls)
validator = validator_cls(schema, registry=SCHEMA_REGISTRY)